Accretion definition, an increase by natural growth or by gradual external addition; growth in size or extent. See more.
Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream. Learn more about how they function and quiz your knowledge at the end.
The bronchioles end in tiny balloon-like air sacs called alveoli. Your body has over 300 million alveoli. The alveoli are surrounded by a mesh of tiny blood vessels called capillaries. Here, oxygen from the inhaled air passes through the alveoli walls and into the blood.After absorbing oxygen, the blood leaves the lungs and is carried to your heart. Your heart then pumps it through your body to provide oxygen to the cells of your tissues and organs.As the cells use the oxygen, carbon dioxide is produced and absorbed into the blood.Your blood then carries the carbon dioxide back to your lungs, where it is removed from the body when you exhale.he bronchioles end in tiny balloon-like air sacs called alveoli. Your body has over 300 million alveoli. The alveoli are surrounded by a mesh of tiny blood vessels called capillaries. Here, oxygen from the inhaled air passes through the alveoli walls and into the blood.